This invention relates generally to apparatus for installing and removing printed circuit boards from a housing and, more particularly, to apparatus of the kind that further function to lock the boards in place.
Printed circuit (PC) boards are a well known form of electrical circuit packaging. Typically, PC boards carry along their lower edge a set of electrical contacts adapted to engage a mating set of contacts carried on a chassis. PC boards can be very large and require the use of a large number of such electrical contacts. As the number of mating electrical connections increases, the force required for inserting the board into the chassis to make the connection increases correspondingly, and can sometimes exceed 100 lbs. In addition to requiring a greater insertion force, the accuracy that is required in mating the electrical contacts is more difficult to achieve because of the greater number of simultaneous contacts that must be made. In addition, the individual electrical contact pins can be easily damaged by improper insertion.
One prior apparatus for installing PC boards with the required force and accuracy is shown in U.S. Pat. No. 4,318,157 to Rank, et al. The disclosed apparatus includes a jack screw that requires the use of a wrench or screwdriver to operate and, therefore, is not considered self-contained. Additionally, when two of such apparatus are mounted on a single PC board, the user must rotate both jack screws simultaneously in order to achieve proper insertion, a process that can be difficult to carry out properly and that can result in improper mating.
Other prior apparatus of this kind utilize levers to load the boards, but they generally provide an insufficient insertion force for use with larger PC boards. These levers often are attached to the PC board close to the edge carrying the electrical connector. This location makes it difficult to combine the lever with other devices, such as those that lock the PC board in place, reduce vibration, and increase heat transfer.
It should, therefore, be appreciated that there is a need for a PC board retaining apparatus that avoids the above difficulties. Ideally, the apparatus should be capable of applying large insertion forces to the PC board's electrical connector, while at the same time providing a high degree of accuracy in aligning the mating electrical connectors. Additionally, the apparatus should be operable without the need for separate tools and should be capable of functioning in combination with other PC board devices, such as those intended to lock the board in place, reduce vibration, and increase heat transfer. These benefits are all provided by the present invention.